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>Date: Sat, 19 Jun 1999 08:33:09 -0300 (ADT)
>From: Michael Boschat <andromed@ATM.DAL.CA>
>To: ASTRO <astro@lists.mindspring.com>
>Subject: [ASTRO] IMO-news: 1999 Beta Taurids Alert - Possible Swarm
Appearance (fwd)
>Sender: owner-astro@brickbat12.mindspring.com
>Reply-To: Michael Boschat <andromed@ATM.DAL.CA>
>
>May be of interest!
>
>Mike
>Halifax Center
>=============================================
>
>------- Forwarded Message
>
>Date: Wed, 16 Jun 1999 15:55:49 +0100
>From: Alastair McBeath <mcbal.gwyvre@virgin.net>
>To: imo-news@imo.net
>Subject: 1999 Beta Taurids Alert - Possible Swarm Appearance
>
>1999 Beta Taurids Alert - Possible Swarm Appearance
>
>>From Alastair McBeath, IMO Vice-President, e-mail:
>vice_president@imo.net
>
>In 1993 David Asher presented a paper to the International Meteor
>Conference in Puimichel [1] describing a theoretical resonant swarm of
>particles within the Taurid/Beta Taurid stream which could account for
>various meteor shower enhancements, increased fireball fluxes and even
>meteoritic impacts associated with the Taurid Complex of meteoroid
>streams, asteroids and comets. He used this theory to suggest times when
>future returns of the proposed "swarm" might lead to increased activity
>from the nighttime Taurid showers active in October-November, and the
>daytime Beta Taurids of June-July. He suggested that 1999 could see a
>return of the swarm during the Beta Taurid activity period, which is the
>purpose of this reminder warning now.
> Results from late October 1998 [2] suggested an enhanced Taurid period
>had been detected by radio and visual observers in the closing days of
>the month, along with an increased flux of minor Taurid fireballs
>(magnitudes -3 to -8). Another of David's predictions for the swarm was
>that a recurrence might be expected in October-November 1998, which may
>well be what was recorded.
> The Beta Taurids are usually assumed to last from about June 5 to July
>17, reaching an ill-defined single maximum around June 28 (solar
>longitude 96.7 degrees (all solar longitudes given here are for eq.
>J2000.0)) from a radiant at approximately alpha = 086 degrees, delta =
>+19 degrees. There is some disagreement in the published data on the
>shower concerning most of these parameters however (cf. [3]). Most
>authors suggest a lengthy, flat maximum occurs in late June to early
>July. Forward scatter radio results from 1994-1997 [4] indicated a
>moderate-strength echo count enhancement occurred between roughly solar
>longitudes 91-93 degrees, with signs of weaker activity bracketing this
>"peak" between solar longitudes 89-99 degrees. It is not clear if this
>activity belongs to the Beta Taurids, nor whether this represents a
>shift in the maximum time by several days if so, but the 89-99 degrees
>spell is at least comparable in length to the Taurid maximum time in
>early November.
> From their orbital parameters, it is clear the Taurids and Beta Taurids
>are linked, either as two encounters by the Earth with the same stream,
>or as two separate streams which follow very similar orbits, so it is
>not unreasonable we may extrapolate details for the Beta Taurids from
>what we know of the Taurids. If we can do this, it is possible any swarm
>enhancement of the Beta Taurids this June might occur up to 5-8 days
>before the expected maximum, following the relative timings of events
>seen last October.
> To identify what happens with the Beta Taurids this year, whether a
>swarm event or not, I would suggest radio observers should be especially
>alert between June 18-19 through to July 2-3 at least (still later in
>July might be better, as some earlier results suggested a Beta Taurid
>maximum around July 2 or 3; this has not been found in data from the
>1990s so far, however), as continuously as possible. This should cover
>whatever the shower produces and also provide non-peak data for
>calibration. Ideally, 24-hour-a-day monitoring should be carried out,
>but if this is not possible, try to make your observing runs at the same
>time every day. The Beta Taurid radiant is above the horizon between
>roughly 03-04h local time to about 18-19h, for northern hemisphere sites
>between approximately 35-55 degrees north near June 28.
> There are likely to be problems because of Sporadic-E interference,
>other atmospheric events (storms, etc.), and potentially Auroral-E as
>activity builds in Solar Cycle 23. Times when any of these occurred
>should also be included in your reports. Furthermore, there is the
>possibility that the June Bootids, which produced their sudden, and
>quite unexpected, outburst on 1998 June 27-28, may recur this year
>(again on June 27-28 if their timing is the same as in 1998). So far, it
>has not been possible to say why the Bootid outburst happened last June,
>so telling when another one might transpire is presently impossible. The
>overlap in radio-visibilities between the Beta Taurids and the June
>Bootids is significant for sites north of about +45 degrees latitude,
>which created problems in analysing the Bootid outburst by radio in
>1998. This means any unexpected radio peak around June 28 this year need
>not have resulted from the Beta Taurids. Only careful analysis of a
>large enough body of data will reveal this.
> Non-radio observers are faced with a very difficult prospect, because
>the centre of the Beta Taurid radiant is just 10 degrees or so west of
>the Sun on June 28. Tropical or near-equator observers might possibly
>see a few slow-moving shower fireballs in the strong predawn twilight an
>hour or two before sunrise at some point during the dates given above,
>if anything unusual happens from the shower this year. As even the outer
>fringes of the radiant will be on or below the horizon however, the
>meteors will probably have exceptionally long paths across the sky.
> For particularly northern hemisphere observers, there is the additional
>possibility that a few daylight fireballs might occur if a swarm
>appearance manifests. This is because the Beta Taurid radiant will be
>high to very high above the horizon for a large part of the day near the
>shower's expected best from such places. Those who routinely handle the
>American DoD satellite reports which feature especially brilliant
>meteors (Zdenek Ceplecha's "superbolides") should pay particular
>attention to any events that occur during the late June to early July
>period as well; an increased flux could represent something unusual from
>the Beta Taurids. Although the nighttime Taurids do not have much of a
>reputation for producing these especially brilliant fireballs, the Beta
>Taurids may be capable of doing so, assuming for example that the major
>clustering event of lunar impacts, detected by the Apollo programme's
>seismometers, of about ten days' duration centred on 1975 June 22 was
>due to this source.
> There are of course no guarantees that anything unusual will happen
>from the Beta Taurids this year, but even establishing that no swarm
>recurrence happened in 1999 June-July with some degree of certainty
>would help refine David Asher's model of the Taurid Complex swarm. Even
>a swarm appearance is not guaranteed to produce spectacularly high rates
>or dozens of bright meteors. If the 1998 late October Taurid event was
>due to a recurrence of the swarm, it should be noted that the visual
>ZHRs from the shower were enhanced only to the level of normal maximum
>rates (combined ZHRs ~9-10; usually no better than ~5-7 in late
>October), while the Taurid fireball percentage was roughly double that
>in normal years.
> Observations should be submitted to all the usual places you routinely
>do, but copies can also be e-mailed to me as well. Please bear in mind
>that I am still most unwell however (as noted in WGN 27:2), so do not
>expect a rapid response. Good luck, and clear, Sporadic-E-free skies for
>your data collection!
>
>References:
>[1] D. Asher, "Meteoroid Swarms and the Taurid Complex", in:
>"Proceedings IMC, Puimichel 1993", ed. P. Roggemans, IMO, 1993,
>pp.88-91.
>
>[2] A. McBeath, "SPA Meteor Section Results: September-October 1998",
>WGN (in press).
>
>[3] G. W. Kronk, "Meteor Showers: A Descriptive Catalog", Enslow, 1988,
>pp.115-118.
>
>[4] A. McBeath, "The Forward Scatter Meteor Year", in: "Proceedings IMC,
>Petnica 1997", eds. A. Knoefel & A. McBeath, IMO, 1998, pp.39-54.
>
>
>
>------- End of Forwarded Message
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